Thank you OldUser. It sounds very reasonable, and yes, I do plan to naturalize at some point. However, my concern is that my second citizenship was not listed in my I-485, because in that form the question about nationality did not include the wording "(provide all that apply)" but now, the form i-751, newest edition of 04/01, 2024, does include the same wording in Question 6 as the edition of 12/31/2019, which you are referring to, "Country of Citizenship or Nationality (provide all that apply)".
So, I'm conflicted about the difference between my I-485 and I-751 filing; this is the only downside of listing the second citizenship now in I-751, which was not listed before in I-485. Based on your comment, I should list my second citizenship in I-751 now even though it will be different from my I-485 filing.
As far as I understand, you and kpmartini also had it different in I-485 (one nationality listed in Q6) versus I-751 (two nationalities listed in Q6), and despite this difference, your I-751 was approved.
It is good to know, very helpful; thank you.